This invention relates to a process for producing 4-amino-3-methyl-N-ethyl-N-(.beta.-hydroxyethyl)-aniline sulfate which is used not only as an intermediate of various azo dyes, medicines, agrochemicals, etc. but also particularly as a developer for color photography.
As processes for synthesizing a p-phenylenediamine derivative from an aniline derivative through a corresponding nitrosation product of the aniline derivative, there are known, for example, a process of reacting sodium nitrite and hydrochloric acid with an aniline derivative in water as solvent to obtain a p-nitrosoaniline derivative, followed by reducing this derivative [for example, J. Am. Chem. Soc., 73, 3100 (1951)], and a process of reacting an alkyl nitrite with an aniline derivative in an aqueous acid suspension, followed by reducing the thus obtained nitroso compound without isolation [U.S. Pat. No. 4,474,987 (Japanese Patent Examined Publication No. 63-53981)]. The former process, however, requires unavoidably a troublesome purification procedure for removal of various by-products because of side reactions during the nitrosation, and gives an insufficient yield. On the other hand, the latter process is superior to the former process in the quality and yield of the product but has various defects, for example, in that the nitrosation reaction by use of the alkyl nitrite is carried out in a heterogeneous system because alkyl nitrites are almost insoluble in water which is used as a solvent, and a large portion of the water used as solvent should be distilled off, because a finally desired acid salt of the p-phenylenediamine derivative is highly water-soluble, resulting in a low work-efficiency. Further, since water alone is used as a solvent in the catalytic reduction of nitrosation product, hydrogen absorption efficiency is poor and a relatively long time is required for the catalytic reduction.
As described above, the conventional processes comprising nitrosation of an aniline derivative at the p-position followed by reduction involve, for example, the following problems: i) a troublesome purification procedure is necessary because of side reactions occurred during the nitrosation, ii) the nitrosation reaction does not proceeds smoothly owing to a heterogeneous reaction system, iii) a long time is required for removing water used as a solvent. All of these problems cause a cost-increase when the processes are put to practical use. Therefore, a more practical production process free from the above problems is desired.